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309 lines
12 KiB
C
309 lines
12 KiB
C
/*
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* Copyright (C) 2003-2005 by Christopher R. Hertel
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* 2015 Freie Universität Berlin
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*
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* This library is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2.1 of the License, or (at your option) any later version.
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*
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* This library is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with this library; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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*/
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/**
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* @ingroup sys_hashes
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* @{
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*
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* @file
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* @brief Implements the MD5 hash algorithm, as described in RFC 1321
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*
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* @author Christopher R. Hertel <crh@ubiqx.mn.org>
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* @author Hauke Petersen <hauke.petersen@fu-berlin.de>
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*
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* @}
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*/
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#include "hashes/md5.h"
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/**
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* @brief In round one, the values of k (which are used to index
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* particular four-byte sequences in the input) are simply
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* sequential. In later rounds, however, they are a bit more
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* varied. Rather than calculate the values of k (which may
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* or may not be possible--I haven't though about it) the
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* values are stored in this array.
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*/
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static const uint8_t K[3][16] = {
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/* Round 1: skipped (since it is simply sequential). */
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{ 1, 6, 11, 0, 5, 10, 15, 4, 9, 14, 3, 8, 13, 2, 7, 12 }, /* R2 */
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{ 5, 8, 11, 14, 1, 4, 7, 10, 13, 0, 3, 6, 9, 12, 15, 2 }, /* R3 */
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{ 0, 7, 14, 5, 12, 3, 10, 1, 8, 15, 6, 13, 4, 11, 2, 9 } /* R4 */
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};
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/**
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* @brief In each round there is a left rotate operation performed as
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* part of the 16 permutations. The number of bits varies in
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* a repeating pattern. This array keeps track of the patterns
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* used in each round.
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*/
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static const uint8_t S[4][4] = {
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{ 7, 12, 17, 22 }, /* Round 1 */
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{ 5, 9, 14, 20 }, /* Round 2 */
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{ 4, 11, 16, 23 }, /* Round 3 */
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{ 6, 10, 15, 21 } /* Round 4 */
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};
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/**
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* @brief There are four rounds of 16 permutations for a total of 64.
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* In each of these 64 permutation operations, a different
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* constant value is added to the mix. The constants are
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* based on the sine function...read RFC 1321 for more detail.
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* In any case, the correct constants are stored in the T[][]
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* array. They're divided up into four groups of 16.
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*/
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static const uint32_t T[4][16] = {
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{ 0xd76aa478, 0xe8c7b756, 0x242070db, 0xc1bdceee, /* Round 1 */
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0xf57c0faf, 0x4787c62a, 0xa8304613, 0xfd469501,
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0x698098d8, 0x8b44f7af, 0xffff5bb1, 0x895cd7be,
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0x6b901122, 0xfd987193, 0xa679438e, 0x49b40821 },
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{ 0xf61e2562, 0xc040b340, 0x265e5a51, 0xe9b6c7aa, /* Round 2 */
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0xd62f105d, 0x02441453, 0xd8a1e681, 0xe7d3fbc8,
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0x21e1cde6, 0xc33707d6, 0xf4d50d87, 0x455a14ed,
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0xa9e3e905, 0xfcefa3f8, 0x676f02d9, 0x8d2a4c8a },
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{ 0xfffa3942, 0x8771f681, 0x6d9d6122, 0xfde5380c, /* Round 3 */
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0xa4beea44, 0x4bdecfa9, 0xf6bb4b60, 0xbebfbc70,
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0x289b7ec6, 0xeaa127fa, 0xd4ef3085, 0x04881d05,
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0xd9d4d039, 0xe6db99e5, 0x1fa27cf8, 0xc4ac5665 },
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{ 0xf4292244, 0x432aff97, 0xab9423a7, 0xfc93a039, /* Round 4 */
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0x655b59c3, 0x8f0ccc92, 0xffeff47d, 0x85845dd1,
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0x6fa87e4f, 0xfe2ce6e0, 0xa3014314, 0x4e0811a1,
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0xf7537e82, 0xbd3af235, 0x2ad7d2bb, 0xeb86d391 },
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};
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/**
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* @brief md5F(), md5G(), md5H(), and md5I() are described in RFC 1321
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*
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* All of these operations are bitwise, and so not impacted by endian-ness.
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* @{
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*/
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#define md5F( X, Y, Z ) (((X) &(Y)) | ((~(X)) & (Z)))
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#define md5G( X, Y, Z ) (((X) &(Z)) | ((Y) &(~(Z))))
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#define md5H( X, Y, Z ) ((X) ^ (Y) ^ (Z))
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#define md5I( X, Y, Z ) ((Y) ^ ((X) | (~(Z))))
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/** @} */
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/**
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* @brief Extract one byte from a 32-bit word
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*
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* A value of 0 for <idx> indicates the lowest order byte, while 3 indicates
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* the highest order byte.
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*/
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#define GETBYTE(L, idx) ((uint8_t)((L >> (((idx) & 0x03) << 3)) & 0xFF))
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/**
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* @brief Permute the ABCD "registers" using the 64-byte <block> as a driver
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*
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* The MD5 algorithm operates on a set of four longwords stored (conceptually)
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* in four "registers". It is easy to imagine a simple MD4/5 chip that would
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* operate this way. In any case, the mangling of the contents of those
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* registers is driven by the input message. The message is chopped and finally
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* padded into 64-byte chunks and each chunk is used to manipulate the contents
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* of the registers.
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*
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* The MD5 Algorithm calls for padding the input to ensure that it is a multiple
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* of 64 bytes in length. The last 16 bytes of the padding space are used to
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* store the message length (the length of the original message, before padding,
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* expressed in terms of bits). If there is not enough room for 16 bytes worth
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* of bitcount (eg., if the original message was 122 bytes long) then the block
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* is padded to the end with zeros and passed to this function. Then *another*
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* block is filled with zeros except for the last 16 bytes which contain the
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* length.
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*
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* Oh... and the algorithm requires that there be at least one padding byte. The
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* first padding byte has a value of 0x80, and any others are 0x00.
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*
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* @param[in|out] abcd Pointer to an array of four unsigned longwords
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* @param[in] block Array of bytes, must be 64 bytes in size
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*/
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static void permute(uint32_t abcd[4], const uint8_t block[64] )
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{
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uint8_t s;
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uint32_t a, b, c, d;
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uint32_t keep_abcd[4];
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uint32_t x[16];
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/* Store the current ABCD values for later reuse */
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for (int i = 0; i < 4; i++) {
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keep_abcd[i] = abcd[i];
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}
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/* Convert the input block into an array of unsigned longs, taking care
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* to read the block in Little Endian order (the algorithm assumes this).
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* The uint32_t values are then handled in host order. */
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for (int i = 0, j = 0; i < 16; i++) {
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x[i] = (uint32_t)block[j++];
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x[i] |= ((uint32_t)block[j++] << 8);
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x[i] |= ((uint32_t)block[j++] << 16);
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x[i] |= ((uint32_t)block[j++] << 24);
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}
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/* This loop performs the four rounds of permutations.
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* The rounds are each very similar. The differences are in three areas:
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* - The function (F, G, H, or I) used to perform bitwise permutations
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* on the registers,
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* - The order in which values from X[] are chosen.
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* - Changes to the number of bits by which the registers are rotated.
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* This implementation uses a switch statement to deal with some of the
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* differences between rounds. Other differences are handled by storing
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* values in arrays and using the round number to select the correct set
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* of values.
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*
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* (My implementation appears to be a poor compromise between speed, size,
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* and clarity. Ugh. [crh]) */
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for (int round = 0; round < 4; round++) {
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for (int i = 0; i < 16; i++) {
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/* <j> handles the rotation of ABCD */
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int j = (4 - (i % 4)) & 0x3;
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/* <s> is the bit shift for this iteration */
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s = S[round][i % 4];
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/* Copy the b,c,d values per ABCD rotation. This isn't really
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* necessary, it just looks clean & will hopefully be optimized
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* away. */
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b = abcd[(j + 1) & 0x3];
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c = abcd[(j + 2) & 0x3];
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d = abcd[(j + 3) & 0x3];
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/* The actual perumation function.
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* This is broken out to minimize the code within the switch(). */
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switch (round) {
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case 0: /* round 1 */
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a = md5F( b, c, d ) + x[i];
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break;
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case 1: /* round 2 */
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a = md5G( b, c, d ) + x[ K[0][i] ];
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break;
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case 2: /* round 3 */
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a = md5H( b, c, d ) + x[ K[1][i] ];
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break;
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default: /* round 4 */
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a = md5I( b, c, d ) + x[ K[2][i] ];
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break;
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}
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a = 0xFFFFFFFF & (abcd[j] + a + T[round][i]);
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abcd[j] = b + (0xFFFFFFFF & ((a << s) | (a >> (32 - s))));
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}
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}
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/* Use the stored original A, B, C, D values to perform
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* one last convolution. */
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for (int i = 0; i < 4; i++) {
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abcd[i] = (abcd[i] + keep_abcd[i]);
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}
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}
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void md5_init(md5_ctx_t *ctx)
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{
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ctx->len = 0;
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ctx->b_used = 0;
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/* The array ABCD[] contains the four 4-byte "registers" that are
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* manipulated to produce the MD5 digest. The input acts upon the registers,
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* not the other way 'round. The initial values are thosegiven in RFC 1321
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* (pg. 4). Note, however, that RFC 1321 provides these values as bytes, not
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* as longwords, and the bytes are arranged in little-endian order as if
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* they were the bytes of (little endian) 32-bit ints. That's confusing as
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* all getout (to me, anyway). The values given here are provided as 32-bit
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* values in C language format, so they are endian-agnostic. */
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ctx->abcd[0] = 0x67452301;
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ctx->abcd[1] = 0xefcdab89;
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ctx->abcd[2] = 0x98badcfe;
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ctx->abcd[3] = 0x10325476;
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}
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void md5_update(md5_ctx_t *ctx, const void *data, size_t len)
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{
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/* Add the new block's length to the total length. */
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ctx->len += (uint32_t)len;
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/* Copy the new block's data into the context block.
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* Call the permute() function whenever the context block is full. */
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for (size_t i = 0; i < len; i++) {
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const uint8_t *d = data;
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ctx->block[ctx->b_used] = d[i];
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(ctx->b_used)++;
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if (64 == ctx->b_used) {
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permute(ctx->abcd, ctx->block);
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ctx->b_used = 0;
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}
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}
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}
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void md5_final(md5_ctx_t *ctx, void *digest)
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{
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uint32_t l;
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/* Add the required 0x80 padding initiator byte.
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* The md5_update() function always permutes and resets the context
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* block when it gets full, so we know that there must be at least one
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* free byte in the context block.
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*/
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ctx->block[ctx->b_used] = 0x80;
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(ctx->b_used)++;
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/* Zero out any remaining free bytes in the context block. */
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for (int i = ctx->b_used; i < 64; i++) {
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ctx->block[i] = 0;
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}
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/* We need 8 bytes to store the length field.
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* If we don't have 8, call permute() and reset the context block. */
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if (56 < ctx->b_used) {
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permute(ctx->abcd, ctx->block);
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for (int i = 0; i < 64; i++) {
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ctx->block[i] = 0;
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}
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}
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/* Add the total length and perform the final perumation.
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* Note: The 60'th byte is read from the *original* <ctx->len> value
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* and shifted to the correct position. This neatly avoids
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* any MAXINT numeric overflow issues. */
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l = ctx->len << 3;
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for (int i = 0; i < 4; i++) {
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ctx->block[56 + i] |= GETBYTE(l, i);
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}
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ctx->block[60] = ((GETBYTE(ctx->len, 3) & 0xE0) >> 5); /* See Above! */
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permute(ctx->abcd, ctx->block);
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/* Now copy the result into the output buffer and we're done */
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for (int i = 0; i < 4; i++) {
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uint8_t *d = digest;
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d[ 0 + i] = GETBYTE(ctx->abcd[0], i);
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d[ 4 + i] = GETBYTE(ctx->abcd[1], i);
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d[ 8 + i] = GETBYTE(ctx->abcd[2], i);
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d[12 + i] = GETBYTE(ctx->abcd[3], i);
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}
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}
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void md5(void *digest, const void *data, size_t len)
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{
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md5_ctx_t ctx;
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md5_init(&ctx);
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md5_update(&ctx, data, len);
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md5_final(&ctx, digest);
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}
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